The crack of a baseball against a wooden bat is a wonderful sound seldom heard today. Too often it's been replaced by the metallic “clink” of an aluminum bat. Baseball has its roots in balls, gloves and shoes made from animal hides, and bats made from trees. It seems an odd place for high tech equipment to intrude. Making a wooden bat returns you and your kids to the sound and feel of real, old-time baseball.
Almost every common wood has been used for bats at one time or another. However, a few species dominate the history of the sport. Traditionally northern ash has been the wood of choice, but currently—at least in professional baseball, —hard maple is equally desirable. Other materials may include bamboo, beech, birch, and hickory wood.
Bat blanks are graded not only for superior performance, but also for safety. A bat made from a graded bat blank is less likely to break in use. Bat blanks are graded differently from regular furniture grade lumber. First, only straight-grained wood from slow-growing trees of moderate size make the grade. The blank should have tight, evenly spaced growth rings and be free of flaws like knots. The best blanks are often split from the log rather than sawn in order to follow the grain perfectly. Extra care is taken in the drying of bat blanks to create an even distribution of moisture throughout the entire thickness.
While wood knots carry visual appeal, they adversely affect wood strength. Wood strength in knots can be assessed in two ways: tensile strength and compressive strength. These measurements provide a prediction as to how much load (weight) wood can safely bear before collapsing. Tensile stress attempts to elongate or expand an object, while compressive stress attempts to shorten or compress an object.
Since knots are defects which weaken lumber, this weakening effect is more serious when the lumber is subjected to forces perpendicular to the grain and/or tension than when under load along the grain and/or compression. Please note that the extent to which wood knots affect the strength of wood depends on their position, size, number, and condition.
As mentioned above, the most common wood for bats is White Ash (Fraxinus americana), a strong wood that has good resistance to impact strength, and is the correct density to make desirable weight baseball bats. The properties have contributed to making White Ash the most popular baseball bat wood for the past 100 years. It is well known that players are supposed to hit “LOGO UP” with an ash bat, so that ball contact is made on the edge-grain in order to prevent “flaking”. Flaking occurs when repeated contact on the flat-grain results in the annual rings separating. Ash is susceptible to flaking because it is a ring porous species, where in a growth ring, pores formed early in the growing season are much larger than those formed later in the growing season.
According to conventional wisdom, ash bats that have approximately 8 to 10 rings per inch are most desirable and are stronger than other bats. FIG. 1 shows data from the Forest Products Laboratory of the United States Department of Agriculture Forest Service in the form of a graph with rings per inch on the x-axis versus modulus of elasticity on the y-axis for green White Ash wood blanks that were tested prior to the 1930's. Note that as the rings per inch increase, the modulus of elasticity of the tested wood drops. The solid vertical lines show a range of approx. 8 to 12 rings per inch, and the large dot is centered at 25 rings per inch. There is about a 20% drop between the data within the solid lines, and the large dot at 25 rings per inch.
FIG. 1 confirms the conventional wisdom that an ash bat with approx. 8 to 10 rings per inch has desirable modulus of elasticity properties and raises the possibility that the range could be expanded out to perhaps 8 to 12 rings per inch.
While ring-porous ash bats need to be hit on the edge grain because the annual rings will “flake” if hit repeatedly on the flat-grain, bats made of maple do not need to be hit on the edge grain, mainly because maple which is a diffuse porous species, which has pores that are essentially uniform within a ring.
In the 1960s, several species of wood were tested by the Forest Products Laboratory of the United States Department of Agriculture Forest Service for toughness (which is similar to impact bending—like a “karate chop” test). This was just a basic research report, but it was perfectly tailored for wood baseball bats and the results were convincing that wood is stronger when contact is made on the flat grain, even ash. The ash handle of a baseball bat is stronger when impact is made on the flat-grain of the barrel, but edge-grain contact is still advocated for ash bats because the annual rings in the barrel will fatigue and separate after repeated hits. The data in FIG. 1 also shows that rupture on the bark side of the wood is stronger than on the opposite face.
Radiography is considered the most cost-effective screening method for the detection of anomalies or weaknesses in wood blanks or billets. However, the resultant radiograph is subject to interpretation by the observer/operator. There are currently operators utilizing radiography to scan blanks or billets but it is observed that there is no system or method that utilizes computer aided detection to display and correlate observations.